1. Field of the Invention
The invention relates to a device and methods for managing bodily fluids in a patient and more particularly to an implantable catheter having an optically useful tip.
2. Description of the Related Art
There are a number of conditions in patients for which it is desirable to add or withdraw fluid. Some fluid management conditions involve the mammalian brain. Within the cranium, gray and white matter is suspended in cerebrospinal fluid and nourished by blood delivered through cerebral arteries. The gray matter has closely spaced cell bodies of neurons, such as in the cerebral cortex, and the underlying white matter contains densely packed axons that transmit signals to other neurons. Human brain tissue has different densities and comprises approximately eighty percent of the intracranial content, with blood and cerebrospinal fluid each normally comprising approximately ten percent.
Cerebrospinal fluid is produced in several connected chambers known as ventricles and typically is renewed four to five times per day. Cerebrospinal fluid in a healthy human flows slowly and continuously through the ventricles, propelled by pulsations of the cerebral arteries. The fluid flows around the brain tissues and the spinal column, and then through small openings into the arachnoid membrane, which is the middle layer of the meninges surrounding the brain parenchyma and ventricles, where the fluid is finally reabsorbed into the bloodstream.
Under normal conditions, bodily mechanisms compensate for a change in fluid volume within the cranium through tissue resilience and by adjusting the total volume of blood and cerebrospinal fluid so that a small increase in fluid volume does not increase intracranial pressure. Similarly, a healthy brain compensates for an increase in intracranial pressure to minimize a corresponding increase in intracranial volume. This volume- and pressure-relationship can be explained in terms of cerebral compliance, which term is intended to include herein the terms elastance and intracranial compliance.
The brain is compliant as long as a person's auto-regulatory mechanism can compensate for any change in volume. As soon as the brain's auto-regulation or compensatory mechanisms fail, blood and cerebrospinal fluid cannot be displaced, and the brain can no longer adapt to any increase in fluid volume. A reduction in cerebral compliance eventually will lead to an undesired increase in intracranial pressure, also known as hydrocephalus. As more fluid volume is added, a threshold is reached beyond which small increases in volume lead to dramatic and unhealthy increases in intracranial pressure.
A typical device to treat fluid conditions such as hydrocephalus is a ventricular catheter disclosed by Watson et al. in U.S. Pat. No. 5,738,666. In one embodiment, ventricular catheter 22 has a slit 60 in a distal tip 58. A terminal end 40 of a rigid introducer cannula 34 is inserted through the slit 60 during final placement of the ventricular catheter within a selected ventricle. A Tuohy-Borst adaptor 32 is secured to the proximal end of the introducer cannula 34. During set-up, a fiber-optic shaft 66 of an endoscope is advanced through the adaptor 32 and the cannula 34 until a fiber-optic terminal end 28 emerges past ventricular catheter terminal end 58 and aligns with introducer terminal end 40. Fiber-optic shaft 66 is then interlocked relative to introducer cannula 34. The aligned tips of the fiber-optic shaft 66 and the introducer cannula are then retracted proximally within catheter 22 during advancement through tissue until a selected ventricle is reached.
In other words, visualization does not occur during navigation of the Watson et al. catheter through the brain tissue and at least some of a selected ventricle. The doctor or other user is “blind” until the fiber-optic shaft is advanced through the slit in the ventricular catheter. Complications which may arise during placement of a ventricular catheter include injury to vascular structures such as the choroid plexus, injury to neurological structures, and improper positioning of the distal tip of the catheter.
There are a number of brain disorders that arise from neurotoxins or other pathogenic substances which can accumulate in cerebrospinal fluid. For example, it has long been recognized that aggregation of the protein amyloid-beta, which can be found in cerebrospinal fluid, contributes to the degenerative condition known as Alzheimer's disease. Microscopic damage to brain tissue leads to atrophy and a general decline in brain function known as dementia.
Delivery of a substance or certain wavelengths of optical radiation may be beneficial for some medical conditions. Introducing one or more compounds to treat Alzheimer's disease is described, for example, by DiMauro et al. in U.S. Patent Publication No. 2010/0286585. Introduction of red light through the cribriform plate portion of a nasal cavity to treat Alzheimer's disease is disclosed in U.S. Pat. No. 7,351,253 by DiMauro et al.
It is therefore desirable to have a simpler and more accurate device and technique for managing bodily fluids, especially cerebrospinal fluid.